During an SN1 reaction, the leaving group departs first, forming a carbocation intermediate. This intermediate is planar and can be attacked by the nucleophile from either side, leading to the formation of two enantiomers in equal amounts, resulting in a racemic mixture.
The stability of the carbocation intermediate plays a crucial role in the extent of racemization. If the carbocation is relatively stable, it can exist for a longer time, increasing the chances of attack by the nucleophile from either side and thus leading to a higher degree of racemization.
Factors such as the nature of the leaving group, solvent, and reaction temperature can influence the stability of the carbocation and hence the extent of racemization.
